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   Ambrosia artemisiifolia (herb)     
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    Taxonomic name: Ambrosia artemisiifolia Linnaeus
    Synonyms: Ambrosia absynthifolia (Michx., 1803), Ambrosia artemisiifolia L. subsp. diversifolia (Piper, 1837), Ambrosia artemisiifolia L. var. jamaicensis (Griseb. 1861), Ambrosia artemisiifolia L. var. octocornis (Kuntze, 1891), Ambrosia artemisiifolia L. var. quadricornis (Kuntze, 1891), Ambrosia artemisiifolia var. artemisiifolia, Ambrosia artemisiifolia var. elatior (Descourt., 1821), Ambrosia artemisiifolia var. elatior f. villosa (Fernald & Griscom, 1935), Ambrosia artemisiifolia var. paniculata (Michx.), Ambrosia diversifolia (Piper), Ambrosia elata (Salisbury, 1796), Ambrosia elatior L., Ambrosia elatior L. var. heterophylla (Muhlenburg ex Willedenow, 1913), Ambrosia glandulosa (Scheele, 1849), Ambrosia heterophylla (Muhlenburg ex Willdenow, 1803), Ambrosia longistylus (Nuttall, 1840), Ambrosia media (Rydberg, 1910), Ambrosia monophylla (Rydberg, 1922), Ambrosia paniculata (Michaux, 1803, Ambrosia simplicifolia (Raeuschel, 1797), Iva monophylla (Walter, 1788)
    Common names: ambroisie à feuille d'armoise (French-France), ambroisie annuelle (French-France), ambroisie élevée (French-France), ambrosia aux feuilles d'armoise (French-France), ambrosia con foglie di atremisia (Italian-Italy), ambrosia de hojas de ajenjo (Spanish), ambrozja bylicolistna (Poland), ambrozja bylicowata (Poland), annual ragweed (English), artemisia del pais (Spanish), Aufrechte Ambrosie (German-Germany), Aufrechtes Traubenkraut (German-Switzerland), bastard wormwood (English-United Kingdom), Beifußambrosie (German-Germany), Beifussblättriges Ambrosie (German-Germany), Beifussblättriges Traubenkraut (German-Germany), beiskambrosia (Norway), bitterweed (English), blackweed (English-Canada), bynke-ambrosie (Danish-Denmark), carrot-weed (English-Canada), common ragweed (English), hay-fever weed (English-Canada), hog-weed (English), Hohes Traubenkraut (German-Germany), kietine ambrozija (Lithuanian-Lithuania), low ragweed (English), malörstambrosia (Sweden), marunatuoksukki (Finland), parlagfu (Hungary), petite herbe à poux (French-Canada), pujulehine ambroosia (Estonia), ragweed (English), roman bitterweed (English-Canada), Roman wormwood (English), römischer Wermut (German-Germany), Shinners ragweed (English-South Korea), short ragweed (English), small ragweed (English), Stalin weed (English-Hungary), stammerweed (English-Canada), stickweed (English-Canada), vadkender (Hungary), vermellapu ambrozija (Latvian-Latvia), wild tansy (English-Canada)
    Organism type: herb
    Ambrosia artemisiifolia is a summer annual herbaceous plant that is native to temperate North America in the United States and Canada. Also commonly known as ragweed this forb establishes easily in human impacted and disturbed areas in high abundance. It is considered an invasive species in Europe, parts of Asia and Australia, although it is not an extremely competitively aggressive species and is mainly considered a noxious weed that interferes with other cultivated crops. The main impact of this plant is the copious amount of pollen produced from male flowers that are allergens to sensitive people, compounding health problems like rhinitis, oculorhinitis, asthma and causing skin irritations.
    Ambrosia artemisiifolia is a summer annual herbaceous plant that is erect, with many branches (AWCNI, undated) and can reach heights between 1-2 metres (NRW, 2007) with a grooved, reddish, hairy stem (Wittenberg, R. (ed.) 2005). The leaves are opposite, compound, and toothed (Wittenberg, R. (ed.) 2005) reaching lengths of 4-10cm long (VTWIG, undated). The tops of the leaves are green and hairy, with white hairs adpressed on the underside of the leaf (Wittenberg, R. (ed.) 2005). Male flowers are green, small, 4-5mm, with bractless flowers arranged in a terminal spike located in the upper portions of the plant (Wittenberg, R. (ed.) 2005), often drooping (AWCNI, undated). The female flowers are located in the axils of the upper leaves, sessile, and inconspicuous in either small clusters or singly (Wittenberg, R. (ed.) 2005). The fruit of the common ragweed is a woody achene, 3-4mm long and 1-2mm wide, with 4-7 spine-like projections, resembling a crown (VTWIG, undated). The leaves are bright green on both sides with whitish nerves. On older plants the lower leaves can be arranged opposite and the upper leaves can be alternately arranged on the stem (C. Bohren., pers.comm., 2007).
    Similar Species
    Artemisia spp.

    Occurs in:
    agricultural areas, ruderal/disturbed, urban areas
    Habitat description
    Ambrosia artemisiifolia is commonly found in ruderal or waste sites associated with frequent and extensive disturbance regimes resulting from human activities. Roadsides, railways, gravel pits, construction sites, agricultural fields, waterways, urban areas, and private gardens are all sites that this species establishes easily and prolifically on (Bohren, 2006). Common ragweed is a pioneer species establishing after disturbance in early successional plant communities (Maupin & Apparicio, 2004). It prefers full sun and warm areas, with nutrient rich and slightly acidic soils (Wittenberg, R. (ed.) 2005) and can tolerate dry soil conditions (Maupin & Apparicio, 2004). The texture of the soil does not play an important role in establishment but the thickness of the organic layer is inversely related to its presence (Maupin & Apparicio, 2004).
    General impacts
    Common ragweed is an abundant seasonal aeroallergen in late-summer to early fall (Wayne et al. 2002) resulting in millions of dollars annually in health care costs and lost labour hours (Bohren, 2006). In studies performed in Europe and North America, approximately 10-15% of the population is sensitive to the pollen of common ragweed (Bohren, 2006) causing rhinitis, oculorhinits, asthma, and dermatitis(Bass et al. 2000). A. artemisiifolia is also considered a weed pest in agricultural crops like sunflower, sugarbeet, corn and other cereal crops (Wittenberg, R. (ed.) 2005). It also displaces native vegetation in its introduced range especially after a disturbance such as overgrazing or construction which put competitive pressures on the native flora (Protopopova et al. 2006). A. artemisiifolia fruits are a food source for the bobwhite quail but can cause illness in livestock that ingest it (USGS-NPWRC, 2006).
    An essential oil of Ambrosia artemisiifolia acts as an antimicrobial, having antibacterial and antifungal compounds (Chalchat et al. 2004).
    Geographical range
    Native range: United States, Canada, Mexico (EPPO, 2000).
    Known introduced range: Europe, Asia, South America, Guatemala, Cuba, Jamaica, Guadeloupe, Martinique, Maritius, Australia, New Zealand, Hawaii (US) (PIER, 2005; EPPO, 2000; Bass et al. 2000; Kil et al. 2004; Ding et al. 2006; Ma & Liu, 2003; Chauvel et al. 2006; Genton et al. 2005; NOBANIS, undated; Bohren, 2006; Protopopova et al. 2006; Dernovici et al. 2006).
    Introduction pathways to new locations
    Agriculture: Another introduction of Ambrosia artemisiifolia is thought to have occurred in France through the cultivation of potatoes and legumes (Chauvel et al. 2006). The plant was intentionally grown and cultivated in Ukraine for medicinal purposes and subsequently escaped from agricultural fields (Protopopova et al. 2006).
    Other: War has been cited as a mechanism of dispersal for this species since disturbance favors its spread and establishment. Horse-fodder for calvary is considered a contaminant source along with depots for stationing troops (Chauvel et al. 2006). In Yugoslavia war was responsible for the spread of A. artemisiifolia into fallow lands (Bohren, 2006).
    Seed contaminant: The seed of Ambrosia artemisiifolia is often found in commercial bird mixes and is considered one of the main ways the species was introduced into several European countries. The species was found in contaminated cereal seed, like sunflower and sorghum and introduced by those means as well (Bohren, 2006).
    Taken to botanical garden/zoo: Ambrosia artemisiifolia was first cultivated in botanical gardens in France and other European countries due to its medicinal properties; several specimens escaped from cultivation and disappeared into natural areas (Chauvel et al. 2006).
    Transportation of habitat material: A common practice in neighbouring countries in Europe, particularly between Switzerland, France and Italy, building construction materials and substrates near borders are exchanged leading to contamination and facilitation by disturbance (Bohren, 2006).

    Local dispersal methods
    Translocation of machinery/equipment (local): The movement and exchange of construction equipment and agricultural machinery are both responsible for spreading the seed of A. artemisiifolia (Bohren, 2006).
    Transportation of habitat material (local): Building construction and the movement of materials favors the spread and establishment of Ambrosia artemisiifolia (Bohren, 2006).
    Water currents: The seed of common ragweed can spread via water currents along riparian corridors (EPPO, 2000).
    Management information
    Preventative measures: Preventing an infestation is the most cost-effective approach to weed control. Preventative measures include maintaining healthy vegetation to inhibit the establishment of common ragweed, detection and surveillance along with proper land management to deter an infestation (NRW, 2007) and prevention of overgrazing, sourcing animal feed and hay, along with commercial agricultural seed (NWR, 2007). Hand-pulling of single plant stands should be combined with early detection and surveillance in areas with beginning infestation (C. Bohren., pers.comm., 2007). European scientists issued a Call for Action in 2008 to motivate responsible authorities to adopt measures to prevent further spread of ragweed in Europe and to control current infestations (C. Bohren., pers.comm., 2008).

    Please follow this link to read the English language version of 'The “Guidelines for management of Ambrosia”, Buttenschøn et al 2009 . The Guidelines are also available in Danish, French, German, Italian and Slovene. The Guidelines have been developed to provide European authorities, private landowners, gardeners, constructors, birdseed producers, trade companies dealing with agricultural products with scientifically based, but simple and operative practical management methods to prevent further invasion and reduce the abundance of common ragweed.

    Please follow this link for detailed information on physical, mechanical, biological, cultural and integrated methods used to control the common ragweed compiled by the IUCN/SSC Invasive Species Specialist Group.

    Common ragweed is a monoecious plant with male and female sex organs occurring in different flowers located on separate areas of the same plant. Flowering period is daylength dependent (Bohren, 2006) and is from early summer to early autumn (Wittenberg, R. (ed.) 2005). This species is self-compatible (Genton et al. 2005), meaning that it can self-fertilise for seed production. The mechanism for pollination is through the wind, since the flowers are not attractive to insects (Genton et al. 2005).
    Lifecycle stages
    Ambrosia artemisiifolia is a summer annual plant. Fruit and seed production begin after fertilisation around the middle of the summer and into the fall. Seeds are shed directly from the parent plant and most seeds land with proximity to the parent plant with a seed rain of 500-7300 seeds/square metre (EPPO, 2006). Seeds enter a dormancy period that requires a cold stratification in order to germinate (Bazzaz, 1970). Germination occurs in the spring with only a portion of the seed bank germinating while the rest of the seeds enter a secondary dormancy period (Bazzaz, 1970). The secondary dormancy of the seed makes this species well adapted at surviving in continuously disturbed sites (Bazzaz, 1970). Seeds have been known to remain viable after 20 years of burial with 85% germination rate (Lewis, 1973).
    Reviewed by: Christian Bohren, Station de recherche Agroscope Changins-Wädenswil ACW Switzerland
    Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
    Last Modified: Wednesday, 17 March 2010

ISSG Landcare Research NBII IUCN University of Auckland